Process of producing alkaline-earth-metal compounds.



F. w. HUBER & R. w. POINDEXTER, JR. PROCESS OF PRODUCING ALKALINE EARTH METAL COMPOUNDS.

APPLICATION FILED JULY 6,1914- Patented Jan. 23,1917.

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-FREDERICK W. HUBER AND ROBERT w. roINDExTEn, roama JR, or LOS YANIGELES, CALI- PROCESS OF PRODUCING ALKALINE-EARTH-METAL COMPOUNDS.

Specification of Letters Patent.

Application filed July 6, 1914. serial No. 849,314.

To all whom it may concern from strontium sulfate, which may be in the form of celestite, which is a mineral appearing in relatively large quantities and which has heretofore not been extensively utilized.

It has been suggested to use strontium oxid or hydroxid in place of lime, in the sugar industry, but heretofore such a process, while simplifying some of the steps of the sugar industry, was not commercially feasible, on' account of the high cost of strontium compounds. In our process, we can greatly reduce the cost of producing strontia from celestite.

We have found that when finely ground strontium sulfate is heated in a reducing flame, to a temperature of from 1200 to 1300 C., the strontium sulfate is reduced to strontium sulfid, which strontium sulfid can be utilized for any desired purpose, for example for the production of strontium hydroxid, which latter operation. may be readily performed by treating the strontium sulfid at a high temperature with steam.

The process may be carried out in anapparatus such as is shown in the accompanying drawing, however, we call attention to the fact that various other forms of apparatus may be employed in carrying out the process.

The figure illustrates a side view, partially in section, of an apparatus suitable for use in carrying out the process.

In said drawing 1 illustrates a rotary inclined kiln of the type commonly employed in the manufacture of Portland cement and similar material.

' 2 represents a hopper through which the celestite or other strontium sulfate, orother alkaline earth sulfate is introduced into the upper end .of the inclined furnace 1. 8 illustrates a suitable burner through which fuel and air are introduced in the form of'a .blast, for the productionof the necessary reducing flame.

The material introduced from the hopper 2 after traveling downwardly through the inclined kiln 1, is discharged at 4, into a" space 5 inclosing the lower end of this'kil'n, and thence into and through a second inclined rotary kiln 6, in which itis treated with steam, at a temperature suflicientl'y high to convert the strontium sulfid, or other alkaline earth sulfid into oxid or hydroxid. This temperature may if desired be in the vicinity of 800 C., and since the sulfid enters the kiln 6 at a temperature ofsubstantially 1200 0., no particular difliculty is found in maintaining the desired high temperature in the kiln 6. At 7 "the finished product is discharged into a casing 8, in which it may be allowed to cool sufficiently, after which it maybe removed, by means for example of a helical conveyer 9, to a suitable leaching and purifying apparatus, or to the storage bin, or elsewhere.

Patented Jan. 23, 1917,

In the inclined furnace 6, the steam reacts with the sulfid, to produce strontium oxid or hydroxid and hydrogen sulfid, the latter [travels backinto the chamber 5, and thence through the kiln 1, thereby aiding in maintaining the reducing atmosphere, in the kiln 1.

During the passage of the hydrogen sulfid through the inclined kiln 1, it is partly burned, to produce free sulfur, which free sulfur, will be in the form of vapor, and

will largely condense out in the dust chamber 10, which may be of any suitable dimensions, and which may be provided with suitable number of bafiies 11, in order to cause the gases to assume a tortuous course. The gases may pass to any suitable gas washer, etc., if desired. The sulfur obviously forms a valuable by-product. The wastegases, after the bulk of the sulfur has settled out, pass by means of-a connection 12, to the stack or chimney, or to a gas washer It will be obvious that sultable rotating means for the kilns 1 and 6 will be provided, mounted. on the standards 13 and 14 respectively.

In the production of the requisite high temperature. the air used in, the blast may be preheated if desiredyby the waste heat of the exit gases, or otherwlse, therebyef fecting a saving of fuel.

The strontium sulfate will preferably be ground to a powder before being introduced into the kiln. The degree of fineness will determine the temperature necessary in the kiln 1, and the length of time necessary to effect the reduction of sulfate to sulfid.

The steam, in its passage through the kiln 6, will become highly superheated by the hot.

strontium sulfid, which greatly facilitates the reaction between these two materials.

We are aware that strontium sulfate has heretofore been mixed with a reducing agent, such as coal, and heatedin a muffle furnace to a temperature of 600 to 800 C., for the purpose of reducing the sulfate to sulfid, but we call attention to the fact that in our process,-no reducing agent is mixed with the strontium sulfate, other than the reducing flame introduced through the burner 3. The reducing flame may be produced by the combustion of powdered coal,

for the reason that in the continuous process a large'yield can be secured.

What we claim is V 1. A-process of producing a sulfid of an alkaline earth metal, which comprises subjecting the sulfate of such a metal, free from admixture with solid fuel, to a reducing flame, at a temperature of about'1200 to 1300" C. 9

2. A process of producing strontium sulfid, which comprises, subjecting strontium sulfate, in a comminuted form to the action of a reducing flame, at a temperature of about 1200 to 1300 0.. I

3. A process of producing strontium-oxygen compounds, which comprises subjecting strontium sulfate to the action of a reducing flame, at a temperature of about 1200 to 1300 C., and thereafter subjecting the hot strontium sulfid, therebyf produced, and

while still in a highly heated condition, to the action of superheated steam,

4. A process of producing-alkaline earth ,j

metal compounds, which comprises sub-- a high temperature, and bringing the gaseous product of said second reaction into contact with the material treated in said first step, to aid in maintaining a reducing atmosphere in said first step.

5. A continuous process of producing strontium-oxygen compounds, which comprises subjecting strontium sulfate, in the form of a moving agitated mass, to contact with a reducing flame at a temperature of about 1200 to 1300 (1, subjecting the hot strontium sulfidthereby produced to the action of steam, and passing the hydrogen sulfid produced in said second step, into con tact with the materials treated in the first step, toaid in maintaining. a reducing atmosphere in said first step; i

' 6. A process of reducing sulfates to sulfids, which comprises subjecting the sulfate unmixed with solid fuel to the action of a reducing flame, at a temperature materially flame, capable of heating said sulfate to a temperature materially above a red heat.

In testimony whereof, I, F. WV. HUBER, have affixed my signature in presence of two witnesses.

FREDERICK w. HUBER.

ROBERT W. POINDEXTER, JR.

Witnesses: HARRY P. H001) Lucius P. GREEN. 

